Creating a real_escape_string() method for systems with magic quotes enabled

The book I'm learning PHP from says that in order to prevent people using things like quotes to alter the query, you should use the real_escape_string function. The author then goes on to say that on some older systems, where magic quotes is enabled, using real_escape_string could end up double escaping some characters, so he creates this function:

<?php
    function mysql_fix_string($conn, $string) {
        if (get_magic_quotes_gpc()) $string = stripslashes($string);
        return $conn->real_escape_string($string);
    }
?>

Would it be okay to turn this into a method in an extended class of the mysqli class? (There isn't any real reason why I wanted to, other than that I wanted to pass in as few arguments as possible.)

If so, is this the right way to do it?

class mysqli_extended extends mysqli {
    public function fix_string($string) {
        if(get_magic_quotes_gpc()) {
            $string = stripslashes($string);
        }
        return $this->real_escape_string($string);
    }
} 

And is this a situation where a static method makes more sense? If so, how could it be rewritten as a static method, and if not, then why?

---

Since I just asked like a million questions, I'll put a summary of them here:

1. Is it okay to create a method for this purpose. (Are there any drawbacks to this?)
2. Is the above code the correct way to do so?
3. Should it be a static method?
4. How would you make it a static method?

Magic quotes has been deprecated as of php 5.3 and is removed in 5.4. I recommend learn php the right way